In the conventional geopolymeric system, geopolymeric conventional materials are prepared by dissolution and polycondensation reaction between the (a) untailored solid reactive powders of alumino-silicate materials and (b) essentially are highly alkaline aqueous solution.
Reference may be made to the article “Sustainable design of geopolymers—Integration of economic and environmental aspects in the early stage of material development authored by M. Weil, E. Gasafi, A. Buchwald and K. Dombrowski, 11th Annual International Sustainable Development Research Conference, Helsilnki, Finnland, 2005; pp 1-14, wherein it is reported that the conventional process of making geopolymeric materials, essentially consist of a silicate aluminate solid component as binding material and an alkaline solution component as alkaline activator. However, the drawbacks of this process are the use of alkali activators in solution form as one of the essential component which results in difficulty in handling the solution.
Reference may be made to article “Acid resistance of fly ash based geopolymer mortars, authored by Suresh Thokchom, Partha Ghosh, and Somnath Ghosh, International Journal of Recent trends in Engineering, 1(6) 2009, pp 36-40, wherein it is reported that mixture of sodium hydroxide and sodium silicate solution were used to activate fly ash for producing geopolymer binder. However, the drawbacks of this process are the use of alkali activators in solution form as one of the essential component which results in difficulty in handling the solution.
Reference may be made to the article “Alkali activated Geopolymers: A Literature Review” authored by Jeffrey C. Petermann and Athar Saeed and Michael I. Hammons; Air Force Research Laboratory Materials and Manufacturing Directorate, July 2010, contract No. FA4819-07-D0001 pp: 1-99, wherein it is reported that in the conventional process of making geopolymeric materials, essentially fly ash or other pozzolona are mixed with the alkaline solutions. However, the drawbacks associated with the process are use of alkali activators in solution form as one of the essential component which results in difficulty in handling the solution. Another drawback associated with the process is use of untailored raw materials resulting in development of products with unpredictable properties.
Reference may be made to article ‘Mechanical and microstructural properties of alkali-activated fly ash geopolymers, Journal of Hazardous Materials, 181(1-3), 2010 pp 35-42 wherein aqueous solutions of Ca(OH)(2), NaOH, NaOH+Na(2)CO(3), KOH and sodium silicate (water glass) of various concentrations were used as alkali activators. It was established that the nature and concentration of the activator was the most dominant parameter in the alkali-activation process. However, the drawbacks associated with the process is use of alkali activators in solution form as one of the essential component which results in difficulty in handling the solution and also the use of untailored raw materials resulting in development of products with unpredictable properties.
Reference may be made to article ‘Fly Ash-Based Geopolymer Mortar Incorporating Bottom Ash, authored by Djwantoro Hardjito, and Shaw Shen Fung, Modern Applied Science, 4 (1), 2010, 44-52, wherein mixture of Potassium Silicate (K2SiO3) solution and Potassium Hydroxide (KOH) solution were used as the alkaline activator. The mixture of fly ash and aggregates was mixed mechanically and Potassium Silicate (K2SiO3) solution and Potassium Hydroxide (KOH) solution were premixed separately. However, the drawbacks associated with the process is use of alkali activators in solution form which results in difficulty in handling the solution and also the use of untailored raw materials resulting in development of products with unpredictable properties. Reference may be made to article “Preliminary study on effect of NaOH concentration on early age compressive strength of kaolin-based green cement” authored by H. Kamarudin, A. M. Mustafa Al Bakri, M. Binhussain, C. M Ruzaidi, M. Luqman, C. Y. Heah, Y. M. Liew, 2011 International Conference on Chemistry and Chemical Process IPCBEE, 10, 2011, pp 18-24 wherein sodium hydroxide was mixed with distilled water to prepare solutions of concentrations 6-14M, cooled to room temperature and mixed with sodium silicate to prepare liquid alkali activator 24 hours before use. However, the drawbacks of the process is use of alkali activators solution which results in difficulty in handling the solution.
Reference may be made to article “Review on fly ash-based geopolymer concrete without Portland Cement” Journal of Engineering and Technology Research authored by Mohd Mustafa Al Bakri, H. Mohammed, H. Kamarudin, I. Khairul Niza and Y. Zarina, 3(1), pp. 1-4, January 2011 wherein it is reported that sodium silicate and potassium hydroxide were used as alkali activators and usually either of this material was mixed with sodium hydroxide to produce the alkaline solution of molarity (M) 7 to 10 M and was prepared a day before it is to be mixed with fly ash and aggregates to prepare concrete. However, the drawbacks of the process is use of alkali activators solution which results in difficulty in handling the solution and also the use of untailored raw materials resulting in development of products with unpredictable properties.
Reference may be made to article “Investigating shrinkage changes of natural pozzolan based geopolymer cement paste” authored by E. Najafi Kani and A. Allahverdi, Iranian Journal of Materials Science and Engineering 8 (3) 2011, pp 50-60 wherein it is reported that sodium hydroxide was added to sodium silicate solution in appropriate quantity to adjust the dosage of activator to prepare geopolymer mixes. However, the drawbacks of the process are again the use of alkaline activator solution which results in difficulty in handling the solution.
Reference may be made to the article “The processing, characterization, and properties of fly ash based geopolymer concrete, M. Mustafa Al Bakri, H. Kamarudin, M. Bnhussain, I. Khairul Nizar, A. R. Rafiza and Y. Zarina, Rev. Adv. Mater. Sci. 30 (2012) 90-97 wherein it is reported that the two major constituents of geopolymer source material consist of alumina-silicate and alkaline liquids. Most commonly used alkaline activators are a mixture of sodium or potassium hydroxide (NaOH, KOH) and sodium silicate or potassium silicate and mixing of the activators 24 hours prior to use was also recommended in the article. However, the drawbacks of the process are use of alkali activators solution which results in difficulty in handling the solution and also the use of untailored raw materials resulting in development of products with unpredictable properties.
Reference may be made to the patent PCT/AU2012/001193 wherein reported is the use of silicate solution and alkali hydroxide for preparation of geopolymer mix. However, the drawbacks of the process is use of alkali activators solution which results in difficulty in handling the solution and also the use of untailored raw materials resulting in development of products with unpredictable properties.
Reference may be made to the article ‘Reactivity, workability and strength of potassium versus sodium-activated high volume fly ash-based geopolymers authored by D. Sabitha, J. K. Dattatreya, N. Sakthivel, M. Bhuvaneshwari and S. A. Jaffer Sathik, Current Science, 103(11), 2012, pp 1320-1327 wherein commercial-grade sodium hydroxide and potassium hydroxide flakes were dissolved in distilled water to obtain the respective alkali solutions one day prior to geopolymer cement preparation to avoid excessive heat resulting from the exothermic reaction. Sodium Silicate and potassium silicate solutions were used as the alkaline activators. However, the drawbacks of the process is use of alkali activators solution which results in difficulty in handling the solution and also the use of untailored raw materials resulting in development of products with unpredictable properties.
Reference may be made to the article ‘Geopolymer Concrete’ Concrete Pavement, CPTP Technology Programme, website, wherein it is reported that user friendly geopolymers which can be used under conditions similar to Portland cement are the current focus of extensive worldwise research. However, the drawbacks associated with production of geopolymer are safety risk associated with the high alkalinity of the activating solution. These facts may limit the practical use of geopolymer concrete.
Reference may be made to the article—Mechanical Properties and Microstructure of Class C Fly Ash-Based Geopolymer Paste and Mortar authored by Xueying Li, Xinwei Ma, Shoujie Zhang and Enzu Zheng′ Materials 2013, 6(4), 1485-1495 wherein class C Fly ash was used to carry out experiments and alkali activator were sodium silicate and sodium hydroxide solution. However, the drawbacks of the process are again use of alkaline activator solution and also safety risk associated with the high alkalinity of the activating solution. The use of untailored fly ash is another drawback of the process which resulting in development of product with unpredictable properties.
Reference may be made to the patent WO 2008113609 A2, wherein the geopolymer coating is two component and before use the liquid component (alkaline agent) and solid component (aluminosilicate material) must be mixed with each other. However, the drawbacks of the process is use of raw materials in two part system for preparation of geopolymer coating i.e alkaline agent in liquid form as one part and solid aluminosilicate material as second part which causes difficulty in practical application. The drawbacks of the conventional processes mentioned in the above articles are: the use of high concentration of alkali activators in solution form with pH in the range of 12-14 ii) generation of heat when water is mixed with alkali activators for preparation of solution. This results in difficulty in handling the solution by unskilled workers while working with geopolymer systems.
From the above mentioned prior art and based on the drawbacks of the conventional process, the various issues to be addressed and problems to be solved are as follows:
The last two decades have witnessed significant achievements in the area of making advanced multifunctional materials and one of them is the development of inorganic geopolymeric materials. However, the development of this unique technology suffers from following drawbacks:
a) Firstly, the work so far carried out in the area of development of geopolymeric materials is basically restricted and is essentially based on the need of two parts system wherein i) highly alkaline solutions act as one part ii) and untailored raw materials act as second part, thereby prohibiting the techno-commercial viability of the conventional geopolymeric materials.
b) Secondly, the use of untailored solid reactive powders of alumino-silicate materials in the conventional geopolymeric process result is non-uniform end products.
c) Since in the conventional geopolymeric system, it is essential to mix both the parts i.e. part one and part two materials in appropriate proportions, there is high risk involved in handling of their highly alkaline solutions.
d) The Application Spectrum of conventional geopolymeric materials is narrow as they have relatively limited resistance to heat, acidic environment and durability aspects. Thus in order to overcome the above raised drawbacks awaited with the prior art, the inventors of the present invention realized that there is new process to provide a versatile geopolymer cement that can be mixed with only water and can be hardened like cement, which is the game changing advancement that will revolutionize the use of geopolymer cementitious materials in construction and infrastructure.